1. Field of the Invention
The present invention relates to a one shot mouldable and curable homogeneous rubber composition having a high Young's modulus.
2. Description of the Prior Art
Conventional rubber compositions composed of rubber and various compounding ingredients have a low Young's modulus, and when it is intended to use the rubber composition in a portion, wherein a high mechanical strength is required, it has been necessary to use the rubber composition in the form of a laminate combined with fibers and other reinforcing materials.
However, it is troulesome to effect laminating and moulding, and moreover, the resulting moulded articles are often poor in the homogeneity. There have been known several rubber compositions composed of ethylene-propylene copolymer, monomer, organic peroxide, and one shot moulded articles prepared therefrom. However, rubber compositions having well-balanced physical properties in such a high level that are aimed in the present invention have never hitherto been obtained. For example, British Pat. No. 896,598 and Journal of the Society of Rubber Industry Japan, 42, 921(1966) disclose methods wherein a rubber composition composed of ethylene-propylene copolymer, divinylbenzene and organic peroxide is heated and cured. However, the resulting cured product is still insufficient in the balance of the Young's modulus, tensile strength and tear energy at room temperature, the retentions of Young's modulus, tensile strength and tear energy at high temperature (about 70.degree.C), the creeps at room temperature and at 70.degree.C, and other physical properties.
The present invention provides a homogeneous one shot mouldable rubber composition, which simultaneously has high Young's modulus, tensile strength, elongation, tear energy and retention of physical properties at high temperature (70.degree.C) and a low creep in a well-balanced state without the use of reinforcing material, such well-balanced physical properties having never been attained without the use of reinforcing material by the conventional rubber compositions.